Explanation of Diagnostic Lights on 3b2/400

[Eric J. Nihill]

In article <1990Nov17.040047.21053 at ox.com> jih at ox.com (John Hritz) writes:
>
>	I have a 3b2/400 that has crashed.  Upon cold start, the power comes
>	up and the diagnostic light blinks 5 times, pauses briefly and then
>	repeats.  The system never checks the floppy, so it is not possible
>	to use the boot disk.  Any info on what this diagnostic light 
>	sequence means would be helpful.  
>


Display			Possible Causes/Solution
-----------------------------------------------------------------------
Red LED pulsing		Unknown problem. The console may be wired
1 time.			incorrectly or there may be other trouble
			not revealed by LED pulses.   Investigate  
			further using diagnostics and the powerup
			trouble shooting chart.

Red LED pulsing		Problem with CPU.
2 times.

Red LED pulsing		Problem with firmware (ROMS).
3 times.

Red LED pulsing		Problem with RAM.
4 times.

Red LED pulsing		Problem with the DUART.
5 times.

Both Red and Green	Reseat Mmemory boards, I/O Backplane. Remove
LEDs on.		feature cards. Try to reboot. Disconnect the
			battery and reconnect, then reboot.     Swap 
			first memory card.

Green LED on, Red	Check to see that the console is connected
LED off after a 	correctly.   It should have a Term/Printer
short time.		Adapter hooked hooked to the  MODEM  port.
			Terminals other than AT&T Teletype may not
			supply DTR as a positive 12 volts.   Usa a
			RS-232-C breakout box to verify, or jumper
			pins 8 to 20 in the Term/Printer Adapter.



Source of information:
	AT&T 3B2 Computer Maintenance Reference Manual, Issue 2.
 	Tel #1-800-432-6600

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